Until now, we have made a series of experimental studies of dilute solution
behavior of typical flexible polymers on the basis of the helical wormlike
(HW) chain model. From an analysis of experimental data obtained for the
polymers including their oligomers in their respective $\Theta $ states, we
have shown that atactic poly($\alpha $-methylstyrene) (a-P$\alpha $MS) with
the fraction of racemic diads $f_{r}$=0.72 tends to retain large and clearly
distinguishable helical portions in dilute solution while atactic
polyetyrene (a-PS) with $f_{r}$=0.59 does not. In this study, we determined
the temperature coefficient d ln$_{0}$/d $T$ of the unperturbed
mean-square end-to-end distance $_{0 }$with $T$ the absolute
temperature from light scattering measurements for a-PS and a-P$\alpha $MS.
It has then been found that d ln$_{0}$/d $T$ is definitely negative
for a-PS but almost vanishes for a-P$\alpha $MS. The results are consistent
with the HW theory prediction.

*This research was partly conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Division of Scientific User Facilities, U.S. Department of Energy.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.MAR.R1.64